CAS supports SAML, specifically SAML 2.0. I would recommend you setup bidirectional Federation Partnerships (IPD->SP and SP->IDP). It also supports many other protocols, so this may not be the only way to achieve this goal.
I am referring current versions of CAS, I do not know if CAS 1.0 supports SAML. CAS is currently on 4.x. I recommend you upgrade your CAS environment, prior to attempting any integration.
I do not have a run-book for SAML integration with CAS, but there are plenty of examples of setting up Federation Partnerships with CA-SSO. I recommend you follow an example, but use CAS as the non CA-SSO entity.